A technology referred to as OpenFlow (OpenFlow) has been proposed in recent years, as shown in Patent Literature 1 and Non Patent Literatures 1 and 2. In the OpenFlow, communication is treated as an end-to-end flow, and path control, failure recovery, load distribution, and optimization are performed for each flow. An OpenFlow switch that functions as a forwarding node includes a secure channel for communication with an OpenFlow controller, and operates according to a flow table in which appropriate addition or rewriting is instructed by the OpenFlow controller. In the flow table, a set of a matching rule (matching rule) to be matched against a packet header, actions (Actions) defining processing content, and flow statistics information (Stats) is defined for each flow (refer to FIG. 13).
Action names and contents of actions are defined in Non Patent Literature 2 (see “3.3Actions”). OUTPUT means outputting a packet to a specified port (interface). SET_VLAN_VID down to SET_TP_DST mean actions that modify the fields of a packet header.
For example, when receiving a first packet (first packet), the OpenFlow switch searches the flow table for an entry having a matching rule (matching rule) that matches header information on the received packet. When the entry that matches the received packet is found as a result of the search, the OpenFlow switch executes the processing content described in the action field of the entry on the received packet. On the other hand, when the entry that matches the received packet is not found as the result of the search, the OpenFlow switch forwards the received packet to the OpenFlow controller over the secure channel, asks the OpenFlow controller to determine the path of the packet based on the transmission source and the transmission destination of the received packet, receives a flow entry implementing this path, and then updates the flow table.
Patent Literature 2 discloses a layer 2 switch including a MAC learning table and a control apparatus for the layer 2 switch. The layer 2 switch comprises a conversion unit for converting VWAN-ID added to a frame into a degenerate VWAN-ID and a restoring unit for restoring the degenerate VWAN-ID added to the frame to the original VWAN-ID. The control apparatus for the layer 2 switch determines one degenerate VWAN-ID corresponding to this VWAN-ID and sets the determined degenerate VWAN-ID in the conversion unit and the restoring unit when the VWAN-ID is registered. According to this publication, the degenerate VWAN-ID is expressed with the number of a value smaller than the number of a value that may be adopted by the VWAN-ID. This layer 2 switch registers an entry including the degenerate VWAN-ID in the MAC learning table, using a MAC learning function.    [Patent Literature 1] International Publication No. WO2008/095010    [Patent Literature 2] International Publication No. WO2006/106588    [Non Patent Literature 1]    Nick McKeown and seven other authors, “OpenFlow: Enabling Innovation in Campus Networks”, [online], [Searched on September 21, Heisei 22 (2010)], Internet <URL: http://www.openflowswitch.org//documents/openflow-wp-latest.pdf>    [Non Patent Literature 2]    “OpenFlow Switch Specification” Version 1.1.0. (Wire Protocol 0x01) [Searched on September 21, Heisei 22 (2010)], Internet <URL: http://www.openflowswitch.org/documents/openflow-spec-v1.0.0.pdf>